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Recently the 360 (Edelbrock Performer Manifold, 600CFM carb, no emissions) in my CJ started running rough, backfiring, constantly running rich. I changed plugs, cap, rotor, no improvements.

I found that both the manifold and ported vacuum went to a connector at the thermostat. I was told that the connecter was really a switch and when the motor is cold the distrubuter advances off the manifold vacuum and once it is hot switches to the ported vacuum. I suspected the valve and bypassed it, connecting the distrubter directly to the ported vacuum on the car. Jeep ran awesome, real snappy, tons of power, felt like I had gone from a 6 to an 8.

Today just for the heck of it I checked the timing. I disconnected the distributer and then plugged the ported vacuum. Connected to the number 1 cylinder and got roughly 18*-20*. So I brought it back down to 12* and the jeep was running rough again, lacked power, and started backfiring. I went back to where I originally was and things were better again. I do not notice the jeep overheating although my temp gauge is not working, I measure the resistance ot ground of the Temp sending unit and get 25 ohms which is normal temp.

I do not notice any pinging or knocking at WOT or when I bog it down at a low RPM. So I have a couple questions.

If an engine has a Cam do you normally advance the timing some? I bought this used and do not know if it has a cam in it (Makes sense it might have the full performer package)

Is it possible that a stretched timing chain could do this? Should I inspect it?

What else do you think? Or is every engine different and if it works go with it?
 

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Normally no with a cam. If fact, often it needs to be backed down a bit -- unless all you want is WOT. The increased A/F charge with more timing advance often leads to ping.

Check your total advance - everything connected, 2500-3000 RPM. Should be around 35 tops.
Then measure with the vacuum disconnected too.
The 3 readings, initial, without, and with, will tell you what the the different systems are doing.

Back to ther initial - wondering if the mark's wrong, damper slipped, wrong damper, wrong pointer?

Being only 10 off I wouldn't worry about it. But lots more than that I would.

Interesting little known fact - an EGR leak, even if it doesn't have an EGR valve - exhaust getting back into the intake a little, - causes it to run bad -- unless you advance the timing waaaay up.
 
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